比较 JavaScript 中两个值的值

Question

I have two csv files, one that contains route information, which will be filled with lines of data for each id where by each line contains multiple stations. An example

id,route
abc,stationA:stationB:stationC

so the route field is delimited by : .

the other csv, contains each station and the latitude and longitudes like so:

stationcode,station name, latitude, longitude 
1,stationA, 44.968046, -94.420307

so basically what I want to do is to find out the latitudes and longitudes the user was on on their route. So basically I will read the user's route to have stations A, B and C, and then I want to retrieve the latitude and longitudes from the second csv.

Below is what I have at the moment:

 $(document).ready(function () {
            var markers = []; // define global array in script tag so you can use it in whole page
            var infowindows = [];

            var lat;
            var lng;

            var myCenter = new google.maps.LatLng(1.3000, 103.8000);
            var mapProp = {
                center: myCenter,
                zoom: 6,
                minZoom: 6,
                mapTypeId: google.maps.MapTypeId.ROADMAP,
                mapTypeControl: true
            };
            //google map object
            var map = new google.maps.Map(document.getElementById("map"), mapProp);

            //change event of input tag where type=file and  id=filename
            // mrt input
            $("#filename").change(function (e) {

                var ext = $("input#filename").val().split(".").pop().toLowerCase();

                if ($.inArray(ext, ["csv"]) == -1) {
                    alert('Upload CSV');
                    return false;
                }

                if (e.target.files != undefined) {

                    var reader = new FileReader();
                    reader.onload = function (e) {

                        var csvval = e.target.result.split("\n");
                        var csvvalue;
                        var infowindow = new google.maps.InfoWindow();

                        for (var i = 0; i < csvval.length; i++) {
                            markers[i] = [];

                            csvvalue = csvval[i].split(",");
                            markers[i][0] = csvvalue[0]; //id

                            lat = csvvalue[2]; //latitude
                            lng = csvvalue[3]; //longitude
                            var stationname = csvvalue[1];
                            var stationcode = csvvalue[0];


                            markers[i][1] = new google.maps.Marker({
                                position: new google.maps.LatLng(lat, lng),
                                map: map
                            });


                        }

                    };
                    reader.readAsText(e.target.files.item(0));
                }

                return false;

            });

            // actual input csv data

            $("#csvname").change(function (e) {

                var ext = $("input#csvname").val().split(".").pop().toLowerCase();

                if ($.inArray(ext, ["csv"]) == -1) {
                    alert('Upload CSV');
                    return false;
                }

                if (e.target.files != undefined) {

                    var reader = new FileReader();
                    reader.onload = function (e) {

                        var val = e.target.result.split("\n");
                        var value;
                        var infowindow = new google.maps.InfoWindow();

                        for (var i = 0; i < val.length; i++) {
                            value = val[i].split(",");

                            // extract the route information (start and stop station
                            var route = value[1];

                            // split route 
                            var routeStations = route.split(":");

                            // compare station name to get lat and lng


                        }

                    };
                    reader.readAsText(e.target.files.item(0));
                }

                return false;

            });

        });

My problem is that I have no idea how to retrieve the latitude and longitudes from the second csv file (station coordinates) using the station name of from the csv with the route data.

Answer 1

As RobG described in the comments:

When parsing the stations CSV file (ie in the callback of $("#filename").change ), at the point where you initialize the station marker, also record the data in a mapping object.

Then when parsing your route CSV file (ie in the callback of $("#csvname").change ), simply refer to your mapping object to retrieve the stations coordinates.

Result:

// Global variables.
var stationsCoordinates = {};

$("#filename").change(function (e) {

    // some code

    markers[i][1] = new google.maps.Marker(/* bla bla */);

    // I do not know if you need stationname or stationcode
    stationsCoordinates[stationcode] = {
        lat: lat,
        lng: lng
    }

});

$("#csvname").change(function (e) {

    // some code

    var routeStations = route.split(":");

    var station;

    for (var i = 0; i < routeStations.length; i += 1) {
        station = stationsCoordinates[routeStations[i]];

        // Do something with that station.
        // Use station.lat and station.lng
    }

});